I have a little project that I need a little advice on. First of all it's a gym. So direct v indirect sound is causing intelligibility issues. I think you'll see the main reason for this when you see the distance from the speakers to the listening area.
Second I'm stuck with existing components for now.
Mackie 1604
Mackie SRM450 x 3
Crown XLS402D Bridged mono for sub (1140W into 4 ohms)
JRX118S 4 ohms
I'm using my DR for EQ, RTA, alignment delay, sub limit, effectively setting the crossover between the srm450 low end and the top of the sub by using filter inserts.
Here's a PDF generated by Kevin from my Visio diagram. It's pretty close to scale. Here is the picture PDF.
Looking West from East end of gym.
The speakers are 17' off the wall.
NE corner.
Listening areas along the North wall.
Facing North wall, East bleachers.
Facing N wall, West Bleachers.
Original speaker rigging.
Facing south from center doorway.
Facing S from center of West bleachers.
OK, don't to this at home.
OK, I'm posting this before I lose it all.
Try to get a mental picture about how the speakers are positioned relative to the listeners. And then apply your knowledge and experience to communicate your thoughts.
All constructive observations or comments are welcome.
I look forward to learning more and seeing this from different perspectives, hopefully bringing a hybrid solution better than one man can attain in a vacuum.
Yes, you could say it's just a gym, but I believe that when we do a job children today need to see adults doing good work with conviction and integrity. They don't have that kind of role model much these days. That is what I think matters about this project. That is one of the most important lessons children will learn from Kevin's project.
I don't envy you on this one. In my head I did some video modification / extrapolation and it appears as though the direct line of fire from the speakers is hitting the blue floor or at best the bottom row. If it is hitting the floor, that is one big first bounce. At that angle your thought of just moving the speakers closer would center the bleachers better. One thought though... Do they use the gym for other events where they put chairs on the floor? If so, that could be a problem with loss of coverage.
If that is not an issue, then why not move the speakers almost on top of the bleachers and almost straight down. Lower volume = less reflection.
One last thought... I think on the old forum I read that (forgive me for not being sure about the facts) either using reverb or delay / echo \"perfectly set using a mathmatical equation\" to \"catch\" the reverberations and cancel them out.
Well, one thing is for sure.. you've got a challenge here... I've had my best luck in rooms like this with my new coaxials that don't have a horn. In this case less is going to be more.. that means the less energy you put in this room the better. There will be a point of degrading quality, and the louder you get the worse it will sound. Wolf, do you have the room mode calculator? It will help identify problem areas. The key here is going to be to get the energy on the audience as much as possible and away from the reflective surfaces. The way the speakers are placed there will be comb filtering. I wonder if a center cluster with some \"blinders\" might not work. By blinders I mean boards that would slip in on each side of the speakers or attach to the rigging that would stick out (and here some experimenting
will be necessary to see if there is a magic size.. I'm sure there would be, but whether or not they work remains to be seen) These boards would limit the 90 deg horizontal pattern and act like a long throw horn. I might suggest since you are taking them down that you try this on the ground and see if it will work. Set a piece of plywood on wither side of the speaker and start with say a foot and walk the room and see if the beam width can be limited. in that fashion.. it will be more effective in the higher frequencies of course and as the speakers get closer to the lo end they will naturally become more omni directional no matter what you do.. but then the HF is the problem were trying to deal with here anyway. BTW when you get new speakers get ones that have very tight limited control patterns.
Next thought, what about a center cluster tightly packed. I use this technique to great effect for POW WOW's in the college gym but I have 4 speakers. It's probably do-able though with three if you use two toword the bleachers ar angle, and one aimed at the opposite wall the bleachers are on... The sub would also be packed into the cluster since the DRPA does not provide enough delay for any alignment.
What is the use projected for this space. What will you be doing.. will the audience always be located on the bleachers? Will there be times when the floor will also hold chairs and people? If the bleachers are the only area that the people will be is it an option to move the speakers to the audience, say 1/2 to 2/3 of the way facing a more radical angle downward?
I guess I need more info here, but I think you need to consider a cluster rather than a spread but one thing is sure I need more info here to make a judgment call on this.
As for Dra's suggestion it was me that postulated that thing about the delaying technique and it is possible to do but certainly not with the DRPA and it would only be useful for a portion of the spectrum.
One thing is certain, I wouldn't reposition those speakers just yet... and you have a heck of a job ahead...
Ok on to the Aux fed sub issue.. I have used the Aux fed sub technique but I like running the subs through the Driverack so I went back to that. I was using an Ashley 4001 analog crossover for the job. I will be reinstituting the Aux fed method with my BRAND SPANKING NEW 4800!!!!WO HOOO!!! I (as was already postulated) enable the hi pass filter, and roll off the lo's on the vocal channels since a lot of low end in the vocals just makes them boomy and muddy sounding. This will DEFINITELY be necessary for you Wolfie...LIMIT THE VOCAL LO END! Using this technique (non Aux fed's with the Driverack) has worked well, but the aux fed method is better. Remember to watch out for 200 and 400 hz they are typical problem areas in reverbrant spaces, and do the room mode calculations and apply that info to deal with those modes in the form of cuts in the eq's.
Kevin, try feeding the headphones directly from the ballanced outs from the auxes routed to the sub masters.. you may find that by simply adding a phone jack converter to a mic cable you can feed the phones directly.
Obviously those speakers are not meant to be flown... But on a good note they are rigged in a fashion (bolted between unistrut with 1/4-20 all-thread rod) that they are probably safe...:) I have seen cabinets that are not manufactured as such,...and someone had modified (screwed eyebolts into them) them to fly... This is very dangerous and could result in a very bad accident followed by a nasty law suite... As you probably know flying cabinets are manufactured specifically to do just that... They have reinforced fly points and forged eyebolts... My point is...once you touch those cabinets you have then transferred the responsible party to yourself...
Before I make any additional comments I would like to ask you the following questions: Do you know what the impedance of those speakers are?... I'm assuming...probably 8 ohms... Also what would you guess the cable distance will be from the amp(s) to the speakers once you decide to relocate them or not... Are you planning on flying those subs?...
OK, this is great. I don't feel quite so lonely when I walk into that gym anymore. : ) It can be a little daunting to be the only person who understands the real challenges.
Thanks for the input! I won't get to address all of it right away, but I plan to get to everything.
First, I'm encouraged that the main things I'm concerned about are exactly the things you all brought up. No outliers.
OK, to Dra's post items:
I thought the same thing, that the speakers are projecting most of their energy to the 'blue floor' and the first row. So I walked the room with an SPL meter alternating between pink and some familar U2. You are correct, the 'sweet spot is about where you predicted and the bleachers, although they have pretty even coverage, do not get the primary energy. You are also correct again, because for events we have put three rows of chairs on the floor. That 'hot' area gets about 2-3 db more than the bleachers. And at the back of the bleachers there is another 2db drop.
Now this leads to one of your other points. How is the room being used? Primarily the large event use is for musical/drama events which puts the staging right below the center and west speakers across from the larger 29' west bleacher section.
This was the case a month ago, when the school did the 'HMS Penifore' (sp?). It didn't work well at all from a sound reinforcment standpoint.
Here are a few observations: Not enough gain before feedback. Major variation in sound quality and intelligibility. From zero to seven open lav microphones interacting. OK, enough said. Incidently this is before I added the sub, so imagine this sound without anything really happening below 200Hz.
So this is why I really wanted to move the speaker 1/2 the distance to the listening area. According to Don Davis, et al, this should increase gain before feedback and give 3-6db more gain. (I can't remember if it's 3 or 6). I think I may do this short term because I need to experiment and find out what if this will help and what it will not help.
Next Tuesday there is going to be a very similar staged event with 5 lavs, one vocal and a track. I would just like to have some gain for that one. Then I can work on other experiments over the summer.
I'm trying to fill in some of the information that is not conveyed in the pictures. I hope this is helpful.
Regardless of where this journey leads, I am glad you have you along.
I can tell from your questions that you are a very apt group. I value that highly. :idea:
I'm glad you asked about the speakers. They are SRM450's and even though they have unistrut bolted all over them they actually to have rigging points all over them for M10x1.25 eyebolts. The same eye bolts used on your 115i's. That entire frame you see around the speaker is unnecessary! The part they got right that I referred to earlier in this little thread was that they used strut to cross the iron above the speaker. I can't talk about this part too long or I will start frothing and stuff. This frame they put on is actually very unsafe. The hardware on the top is not only scary, but it is structurally not sound. The hardware at the top of the speaker is actually in such an orientation that the fasteners can't be tightened all the way. OK, I'm starting to froth. That's another reason I want to move them. I have the same saftey concerns you have. I may post a picture close up when they come down. But no matter what we decide acoustically, the speakers need to be completely re-fitted with rated eyebolts and a safety cord on each. Thanks for confirming that safety is definitely part of our responsibility.
OK, onto speaker cable and amp distance. These speakers are 'powered'. They contain an amplifier inside them. You basically send them a line level and plug them in. They also have crossover and some protection/limiting, which by the way you really don't want to hear what they sound like when they go there.
OK, my brain is leaking onto the floor. I'll check in later or tomorrow.
Bless you all for assisting with this. I hope to get to Gadget's points next. I've heard a saying that goes something like this, a burden shared is half a burden. I'm not entirely sure I agree with the math, but the sentiment is right on!
Take care guys!
And thanks again for the support and insight! This is a blast!
Hmmm...\"The input signals are crossed over before they reach the amplifiers\"... \"This removable plate provides access to install future access modules\"... I know this sounds very a-typical but I wouldn't hesitate on looking at the possibility of by-passing the speaker's active crossovers, etc...and wiring direct to the amps from the DR260... It seems to me you would then have much more flexibility, no redundant filtering, limiting, etc.,...and complete tuning control from one accessible and superior DSP...
I love this post. You are truly a perfectionist in the most admirable way.
Here I'm trying to make sure my speakers don't fall on someone or feedback and you are already working on a way to improve the internal crossover and therefore the sonic quality at the source.
I agree with you totally. I think the DR would do a much better job then the guts that are already in these. I'd also like the extra control that would give me.
Sometimes these powered speakers in general are called 'speaker on a stick'. Probably because when you use them you simply put them on a speaker stand, plug them in and turn them on. No knowledge of amps, crossovers or anything to run them. My experience with them is that they are sort of a dumbed down design with the main purpose being self preservation. In other words they are designed so they don't blow up. This design goal necessarily compromises other aspects of their performance.
I've had a similar experience with a powered JBL sub. I did an A-B test with the powered sub and the same sub driver/cab with an amp and DR260. The difference in the sound quality you could get out of the more complicated setup was well worth the effort of setup. There was no comparison and I'm not an expert on this stuff. So I guess I've already proved that your theory is correct.
Anyway I think powered speakers in general should be called McSpeakers. Sort of Fast Food sound that isn't very good for you.
Could you explain briefly why horns don't work well in this space?
I have another install where a guy mentioned horns not being a good idea and I'm just wanting to understand a little about how horns play in an acoustic space, etc.
Could you explain briefly why horns don't work well in this space?
Wolfgong,...I'm going to take a stab in the dark here and guess that one of his concerns is: the horns on those speakers disperse sound at 90deg horizontally and most probably 50deg vertically... I don't see the vertical dispersion mentioned in the manual... I can imagine a horizontal 90deg angle coming from the center of each of those horns... Eventually those right angles from each speaker will overlap each other... The problem areas are where the speaker coverage’s overlap... This is where the comb filtering begins - certain frequencies cancel each other out and create dead spots (fingers)... Oh yea...I got to experience phenomenon first hand!... Another concern might be that the horizontal dispersion angle is much too wide for the coverage distance... Can you move those cabinets forward closer to the audience…say by 1/3rd to 1 half??? If you have to cover the entire gym then the center cluster suggestion would be your best bet I think... This drawing shows the original 90 X 50deg dispersion angles of the JRX115i in our youth room… If I didn’t follow Gadget’s suggestion and butt those speakers right up next to each other it would have been a soni-logical nightmare…
No need to apologize. I continue to learn from your insights. Plus it validates that I'm not yet losing my mind. : )
The power is out at the school today, so I won't be able to refit until that comes back on line. It's a planned outage for the church construction going on next door.
No Kevin you are correct and one of the problems with intelligibility is those areas of comb filtering, but my reason for saying that horns are bad in reverberant spaces is that they beam... that is to say that they direct the energy into a beam that has the higher frequencies bouncing all over the place. This beaming is exacerbated by the wide 90 deg pattern as this spill sound all over the place and makes pattern control difficult and makes it harder to get the sound on the audience and off the reverberant surfaces. The best thing here would be to get some treatment on those walls, use the room mode calculator to visualize the primary and secondary and even to a lesser degree the third order modes and try and limit the amount of energy to what you need and not exceed the rooms \"point of no return\". The point where the room starts to rebel and that any further pushing of the system provides negative results. BTW every indoor space has this point.. it isn't just spaces that have an echo potential.
I would try the center cluster with the focus on two units hung in such a manner that the energy can be focused on the second or third row of the bleachers.. the chairs on the floor should still get coverage and the energy will be on the bodies... don't overlap the coverage if possible, then aim the third speaker back at the other end of the gym and focus the center sweet spot on the point that the floor and wall meet... that should help break up the waves a little bit. You will want to control that one separately if possible. Put the sub up there too, and be careful with the gas pedal on those subs, but centrally located the sub should give its best performance possible. Get the kids to make some of those hanging banner type hangings that you often see in churches using some thick absorptive cloth like coarse canvas perhaps backed by thin foam or ceiling tiles backwards so that the glass face is toward the cloth if lighter weight material is used. .. I have some plans somewhere for some inexpensive traps and things.. I'll see if I can find them.. But the thing is with the hangings they can be taken down easily if the space is multi purpose and they couldn't be permanent..which is likely in some spaces we play right?
Wolfie,
3 rows in front of the bleachers for plays and such. Probably very close to the stage area, right? I dont think I would be concerned about aiming / moving the speakers behind them. They are within regular vocal projection, assuming that their teacher has told them that they're in a play and have to TALK LIKE THIS. Better that 1/2 the people hear really well than all hear skwat. Some times you have to live within the parameters that you're given. And I know that if I were in your shoes now, I'd be pulling my hair out because I expect nothing less than perfection, even if it's not possible.
Good luck,
I'll have to digest what you have said for a bit. I like the idea of a center cluster.
Dra -
You pegged my sentiments exactly on the chair seating area. The stage is almost right by the front row and yes the kids better project their voices. Plus the overhead speakers will add some to those setting in the chairs. The way things are now, we are basically sacraficing the majority of listeners for a few people right off of the stage area. I appreciate your ability to extrapolate this information into very useful observations. You've got a real nack for that.
I'm gonna go check and see if the power is on in the gym.
Here is a brief explanation that might help for now till I can look closer at your room..
Room Dimensions
If you have not yet built a room, or you're about to refinish a space such as a basement, you can do a \"what if\" analysis to determine the room dimensions that will create the fewest problem frequencies. This is why I included a row at the bottom of the spreadsheet that flags problem frequencies and places the total count in cell B27. The \"what if\" analysis procedure begins with the Modal Distribution table and the Ceiling Calculator table. (A good example is described in the March/April '99 \"HTA.\") Alternatively, you can just start entering numbers (in inches) into cells C4 through C6 to look for dimensions that minimize the number of problem frequencies.
If you already have a home-theater room, you can just plug in its dimensions (in inches) into cells C4 through C6; the spreadsheet does the rest. One caveat: Make sure you follow the advice in the November '98 \"HTA\" on how to measure the size of your room. The dimensions in the spreadsheet I've provided are the ones from the \"As Built\" theater in the March/April '99 \"HTA\" with the seating position 1/3 of the way from the back wall, side wall, and floor.
As Built
Room Dimensions 294.5 x 294.5 x 147 inches (L x W x H)
Distance from each wall 98.17 x 98.17 x 49.00 inches (Back x Side x Floor)
Keep in mind that the problem frequencies in row 27 are only a problem if the seating position puts the listener in a null or peak for them. Of course, if there are many problem frequencies (such as the 19 instances in the \"As Built\" dimensions), it is difficult or impossible to pick a good seating position. The number of problem frequencies can be significantly reduced if the room's dimensions are chosen well to begin with.
Placement of Seats
Once you've determined the proper room dimensions, you can figure out good spots to place your seats. Enter the seating distance from the back wall, side wall, and floor into cells C12 through C14. The placement of the seating makes a big difference in the sound because different frequencies have peaks and nulls in different spots in your room. To try this out, enter into the spreadsheet the following dimensions (they're from my own home theater):
My Home Theater
Room Dimensions 224.5 x 165.5 x 94.375 inches (L x W x H)
Distance from each wall 75 x 83 x 32 inches (Back x Side x Floor)
My head is positioned one third of the room's length from the back of the room, exactly in the middle of the room's width, and approximately one third of the height above the floor. For my room and seating position, the following frequencies have peaks at my main listening position:
When choosing seat locations, try to avoid positions at which a frequency has a double or triple peak. The January '99 \"HTA\" discusses a room with several such peaks. My seating position has no double or triple peaks at all. I have included a table in the spreadsheet that automatically calculates the double and triple peaks. If you're interested in these calculations, they start in cell AJ86.
Placing the listener in a null for a particular frequency is even more problematic than a peak. As described in the January '99 \"HTA,\" if a listener sits in a null, there is no way to compensate for this. An equalizer can be used to reduce peaks, but you can't boost the frequency in a null.
Again, consider \"My Home Theater\" dimensions and seating position. The seating position is exactly in the middle of the room's width. The diagram on page 48 of the January '99 \"HTA\" shows the peaks and nulls for the first eight axial modes. It is clear that the halfway point in a room includes nulls at the 1st, 3rd, 5th, and 7th harmonics for that dimension.
You must avoid seating positions at any nulls. By selecting the right seating position (even if you have a room that is merely okay acoustically), you can achieve better sound. My seating position coincides with nulls at several frequencies, so I am looking at ways to change my seating position relative to the width of the room. I have included a table that automatically calculates single, double, and triple nulls.
Both of praise teams are going to practice with our new desk today...in hopes for using it in this evening's big kick-off bonanza... I'm not going to have time to re-set the gain structure, have everything perfect, and to be totally comfortable with the new board...so I'm getting a little nervous... Please PRAY FOR ME!...:)
Remember you're not reinventing the entire gain structure here. So don't make the anxiety more than it needs to be. Remember also that you know what you are doing. You've proved that already. This bit of adjustment will be easy by comparison. I also think you will be delighted with how easy it is to rough in the sound with your new desk. You've made a good choice there and you will see why by going through this process.
Here's the deal... I was able to duplicate problem twice and then isolate it today... It appears that the power supply in the new mixer is bad... I spoke with the manufacturer (Allen & Heath) tech-support and they asked me to return it for a new unit via the distributor... I called the distributor and they told me I purchased the last unit they had in stock... The distributor is contacting Allen & Heath to see how they can get us a replacement unit ASAP...
I thank you very much for your support,...and for using your valuable time in helping me work the problem...:)
Did they give you any indication if the problem you had was a "lot" or "batch" problem? Things like that worry me any time I get a "bad" one.
Hello Dra,
They told me they have never experienced this problem before... The power supply goes bad after the unit has been turned-on for a while...like two to four hours... Then if the unit is turned-off for a couple minutes and then turned back on it will run for another two hours...
Kevin, try feeding the headphones directly from the ballanced outs from the auxes routed to the sub masters.. you may find that by simply adding a phone jack converter to a mic cable you can feed the phones directly.
Hello Gadget,
I tried this but I couldn't get enough volume for the drummer due to the distance... I think the following might be the solution to our problem: http://www.rolls.com/products/pm52.php
I contacted Rolls directly and covered my bases ie...amp wattage and impedance, headphone impedance, etc.,...and they claim this puppy is very robust and will handle practically anything I throw at it...
Just a suggestion, but perhaps we should move Wolfies install to a different thread? This puppy is approaching biblical proportions.. as to what happened I don't know kevin? Perhaps we were spammed? Connie didn't tell me of anything when you saw all those posts.. perhaps she just handled it.
:shock:
I'm talking with her now to see if I can't get a \"READ THIS BEFORE POSTING\" banner so we can address some of the more problematic areas of the \"newbie\" posters.. like lack of info...some primers perhaps, links to the old forum, and training vids.. any suggestions what you would like to see?
Gadget, I agree. When posts get long it is hard to pull info if the topic keeps changing gears (and locations).
1- How to do a generic custom set-up for speakers and amps.
2- How & why to do a gain structure.
3- How to use PEQ's to \"tune\" problem passive cabs.
4- How to properly set x-overs for different cab combos. How to determine the Lo-cut / Hi-pass filter.
5- How & why to use output limiters.
6- How to eliminate feedback.
7- DRPA vs DR260
8- Complete list of manufacturer speaker tunings for passive cabs. (empty with a brief explanation why)
I'm fine with it,...even though I really enjoy the company...:)
A few more suggestions:
9- How to time align your mains and subs (I would enjoy writing something on that)
10- How to incorporate PEQ in suppressing feedback
11- How to map-out speaker placement for optimum sound quality
12- How to calculate \"insertion loss\" and proper wire sizing for 8-ohm, 4-ohm, or 2-ohm speaker runs (I would enjoy writing something on that)
Comments
I have a little project that I need a little advice on. First of all it's a gym. So direct v indirect sound is causing intelligibility issues. I think you'll see the main reason for this when you see the distance from the speakers to the listening area.
Second I'm stuck with existing components for now.
Mackie 1604
Mackie SRM450 x 3
Crown XLS402D Bridged mono for sub (1140W into 4 ohms)
JRX118S 4 ohms
I'm using my DR for EQ, RTA, alignment delay, sub limit, effectively setting the crossover between the srm450 low end and the top of the sub by using filter inserts.
Here's a PDF generated by Kevin from my Visio diagram. It's pretty close to scale. Here is the picture PDF.
http://www.teamaai.net/kevin/jay/GymMeasurements.pdf
While you digest this, I will start loading pictures in to the thread here.
I'm repositioning the speaker tomorrow so they align to the listening areas and are 1/2 the distance that they are now.
I'm swag'ing the rigging down angle. The SRM450's are 90 H x45 V.
Please remember, don't shoot the messenger!
Looking West from East end of gym.
The speakers are 17' off the wall.
NE corner.
Listening areas along the North wall.
Facing North wall, East bleachers.
Facing N wall, West Bleachers.
Original speaker rigging.
Facing south from center doorway.
Facing S from center of West bleachers.
OK, don't to this at home.
OK, I'm posting this before I lose it all.
Try to get a mental picture about how the speakers are positioned relative to the listeners. And then apply your knowledge and experience to communicate your thoughts.
All constructive observations or comments are welcome.
I look forward to learning more and seeing this from different perspectives, hopefully bringing a hybrid solution better than one man can attain in a vacuum.
Yes, you could say it's just a gym, but I believe that when we do a job children today need to see adults doing good work with conviction and integrity. They don't have that kind of role model much these days. That is what I think matters about this project. That is one of the most important lessons children will learn from Kevin's project.
Many Thanks!
If that is not an issue, then why not move the speakers almost on top of the bleachers and almost straight down. Lower volume = less reflection.
One last thought... I think on the old forum I read that (forgive me for not being sure about the facts) either using reverb or delay / echo \"perfectly set using a mathmatical equation\" to \"catch\" the reverberations and cancel them out.
My penny any way,
DRA
Well, one thing is for sure.. you've got a challenge here... I've had my best luck in rooms like this with my new coaxials that don't have a horn. In this case less is going to be more.. that means the less energy you put in this room the better. There will be a point of degrading quality, and the louder you get the worse it will sound. Wolf, do you have the room mode calculator? It will help identify problem areas. The key here is going to be to get the energy on the audience as much as possible and away from the reflective surfaces. The way the speakers are placed there will be comb filtering. I wonder if a center cluster with some \"blinders\" might not work. By blinders I mean boards that would slip in on each side of the speakers or attach to the rigging that would stick out (and here some experimenting
will be necessary to see if there is a magic size.. I'm sure there would be, but whether or not they work remains to be seen) These boards would limit the 90 deg horizontal pattern and act like a long throw horn. I might suggest since you are taking them down that you try this on the ground and see if it will work. Set a piece of plywood on wither side of the speaker and start with say a foot and walk the room and see if the beam width can be limited. in that fashion.. it will be more effective in the higher frequencies of course and as the speakers get closer to the lo end they will naturally become more omni directional no matter what you do.. but then the HF is the problem were trying to deal with here anyway. BTW when you get new speakers get ones that have very tight limited control patterns.
Next thought, what about a center cluster tightly packed. I use this technique to great effect for POW WOW's in the college gym but I have 4 speakers. It's probably do-able though with three if you use two toword the bleachers ar angle, and one aimed at the opposite wall the bleachers are on... The sub would also be packed into the cluster since the DRPA does not provide enough delay for any alignment.
What is the use projected for this space. What will you be doing.. will the audience always be located on the bleachers? Will there be times when the floor will also hold chairs and people? If the bleachers are the only area that the people will be is it an option to move the speakers to the audience, say 1/2 to 2/3 of the way facing a more radical angle downward?
I guess I need more info here, but I think you need to consider a cluster rather than a spread but one thing is sure I need more info here to make a judgment call on this.
As for Dra's suggestion it was me that postulated that thing about the delaying technique and it is possible to do but certainly not with the DRPA and it would only be useful for a portion of the spectrum.
One thing is certain, I wouldn't reposition those speakers just yet... and you have a heck of a job ahead...
Ok on to the Aux fed sub issue.. I have used the Aux fed sub technique but I like running the subs through the Driverack so I went back to that. I was using an Ashley 4001 analog crossover for the job. I will be reinstituting the Aux fed method with my BRAND SPANKING NEW 4800!!!!WO HOOO!!! I (as was already postulated) enable the hi pass filter, and roll off the lo's on the vocal channels since a lot of low end in the vocals just makes them boomy and muddy sounding. This will DEFINITELY be necessary for you Wolfie...LIMIT THE VOCAL LO END! Using this technique (non Aux fed's with the Driverack) has worked well, but the aux fed method is better. Remember to watch out for 200 and 400 hz they are typical problem areas in reverbrant spaces, and do the room mode calculations and apply that info to deal with those modes in the form of cuts in the eq's.
Kevin, try feeding the headphones directly from the ballanced outs from the auxes routed to the sub masters.. you may find that by simply adding a phone jack converter to a mic cable you can feed the phones directly.
Have a good day gents...
Gadget
Obviously those speakers are not meant to be flown... But on a good note they are rigged in a fashion (bolted between unistrut with 1/4-20 all-thread rod) that they are probably safe...:) I have seen cabinets that are not manufactured as such,...and someone had modified (screwed eyebolts into them) them to fly... This is very dangerous and could result in a very bad accident followed by a nasty law suite... As you probably know flying cabinets are manufactured specifically to do just that... They have reinforced fly points and forged eyebolts... My point is...once you touch those cabinets you have then transferred the responsible party to yourself...
Before I make any additional comments I would like to ask you the following questions: Do you know what the impedance of those speakers are?... I'm assuming...probably 8 ohms... Also what would you guess the cable distance will be from the amp(s) to the speakers once you decide to relocate them or not... Are you planning on flying those subs?...
Kevin
Thanks for the input! I won't get to address all of it right away, but I plan to get to everything.
First, I'm encouraged that the main things I'm concerned about are exactly the things you all brought up. No outliers.
OK, to Dra's post items:
I thought the same thing, that the speakers are projecting most of their energy to the 'blue floor' and the first row. So I walked the room with an SPL meter alternating between pink and some familar U2. You are correct, the 'sweet spot is about where you predicted and the bleachers, although they have pretty even coverage, do not get the primary energy. You are also correct again, because for events we have put three rows of chairs on the floor. That 'hot' area gets about 2-3 db more than the bleachers. And at the back of the bleachers there is another 2db drop.
Now this leads to one of your other points. How is the room being used? Primarily the large event use is for musical/drama events which puts the staging right below the center and west speakers across from the larger 29' west bleacher section.
This was the case a month ago, when the school did the 'HMS Penifore' (sp?). It didn't work well at all from a sound reinforcment standpoint.
Here are a few observations: Not enough gain before feedback. Major variation in sound quality and intelligibility. From zero to seven open lav microphones interacting. OK, enough said. Incidently this is before I added the sub, so imagine this sound without anything really happening below 200Hz.
So this is why I really wanted to move the speaker 1/2 the distance to the listening area. According to Don Davis, et al, this should increase gain before feedback and give 3-6db more gain. (I can't remember if it's 3 or 6). I think I may do this short term because I need to experiment and find out what if this will help and what it will not help.
Next Tuesday there is going to be a very similar staged event with 5 lavs, one vocal and a track. I would just like to have some gain for that one. Then I can work on other experiments over the summer.
I'm trying to fill in some of the information that is not conveyed in the pictures. I hope this is helpful.
Regardless of where this journey leads, I am glad you have you along.
I can tell from your questions that you are a very apt group. I value that highly. :idea:
Good to hear from you!
I'm glad you asked about the speakers. They are SRM450's and even though they have unistrut bolted all over them they actually to have rigging points all over them for M10x1.25 eyebolts. The same eye bolts used on your 115i's. That entire frame you see around the speaker is unnecessary! The part they got right that I referred to earlier in this little thread was that they used strut to cross the iron above the speaker. I can't talk about this part too long or I will start frothing and stuff. This frame they put on is actually very unsafe. The hardware on the top is not only scary, but it is structurally not sound. The hardware at the top of the speaker is actually in such an orientation that the fasteners can't be tightened all the way. OK, I'm starting to froth. That's another reason I want to move them. I have the same saftey concerns you have. I may post a picture close up when they come down. But no matter what we decide acoustically, the speakers need to be completely re-fitted with rated eyebolts and a safety cord on each. Thanks for confirming that safety is definitely part of our responsibility.
OK, onto speaker cable and amp distance. These speakers are 'powered'. They contain an amplifier inside them. You basically send them a line level and plug them in. They also have crossover and some protection/limiting, which by the way you really don't want to hear what they sound like when they go there.
OK, my brain is leaking onto the floor. I'll check in later or tomorrow.
Bless you all for assisting with this. I hope to get to Gadget's points next. I've heard a saying that goes something like this, a burden shared is half a burden. I'm not entirely sure I agree with the math, but the sentiment is right on!
Take care guys!
And thanks again for the support and insight! This is a blast!
Here's a link to the speaker manual.
http://www.mackie.com/pdf/srm450_om.pdf
I love this post. You are truly a perfectionist in the most admirable way.
Here I'm trying to make sure my speakers don't fall on someone or feedback and you are already working on a way to improve the internal crossover and therefore the sonic quality at the source.
I agree with you totally. I think the DR would do a much better job then the guts that are already in these. I'd also like the extra control that would give me.
Sometimes these powered speakers in general are called 'speaker on a stick'. Probably because when you use them you simply put them on a speaker stand, plug them in and turn them on. No knowledge of amps, crossovers or anything to run them. My experience with them is that they are sort of a dumbed down design with the main purpose being self preservation. In other words they are designed so they don't blow up. This design goal necessarily compromises other aspects of their performance.
I've had a similar experience with a powered JBL sub. I did an A-B test with the powered sub and the same sub driver/cab with an amp and DR260. The difference in the sound quality you could get out of the more complicated setup was well worth the effort of setup. There was no comparison and I'm not an expert on this stuff. So I guess I've already proved that your theory is correct.
Anyway I think powered speakers in general should be called McSpeakers. Sort of Fast Food sound that isn't very good for you.
LOL
Thanks for the post!
Could you explain briefly why horns don't work well in this space?
I have another install where a guy mentioned horns not being a good idea and I'm just wanting to understand a little about how horns play in an acoustic space, etc.
Thanks!
http://www.teamaai.net/kevin/Youth/Yout ... Layout.pdf
Sorry,...My bad...I just now had the time to go back and read "everything"...:) I'm going to keep my mouth shut and learn from the pros...:)
Kevin
No need to apologize. I continue to learn from your insights. Plus it validates that I'm not yet losing my mind. : )
The power is out at the school today, so I won't be able to refit until that comes back on line. It's a planned outage for the church construction going on next door.
Cheers!
No Kevin you are correct and one of the problems with intelligibility is those areas of comb filtering, but my reason for saying that horns are bad in reverberant spaces is that they beam... that is to say that they direct the energy into a beam that has the higher frequencies bouncing all over the place. This beaming is exacerbated by the wide 90 deg pattern as this spill sound all over the place and makes pattern control difficult and makes it harder to get the sound on the audience and off the reverberant surfaces. The best thing here would be to get some treatment on those walls, use the room mode calculator to visualize the primary and secondary and even to a lesser degree the third order modes and try and limit the amount of energy to what you need and not exceed the rooms \"point of no return\". The point where the room starts to rebel and that any further pushing of the system provides negative results. BTW every indoor space has this point.. it isn't just spaces that have an echo potential.
I would try the center cluster with the focus on two units hung in such a manner that the energy can be focused on the second or third row of the bleachers.. the chairs on the floor should still get coverage and the energy will be on the bodies... don't overlap the coverage if possible, then aim the third speaker back at the other end of the gym and focus the center sweet spot on the point that the floor and wall meet... that should help break up the waves a little bit. You will want to control that one separately if possible. Put the sub up there too, and be careful with the gas pedal on those subs, but centrally located the sub should give its best performance possible. Get the kids to make some of those hanging banner type hangings that you often see in churches using some thick absorptive cloth like coarse canvas perhaps backed by thin foam or ceiling tiles backwards so that the glass face is toward the cloth if lighter weight material is used. .. I have some plans somewhere for some inexpensive traps and things.. I'll see if I can find them.. But the thing is with the hangings they can be taken down easily if the space is multi purpose and they couldn't be permanent..which is likely in some spaces we play right?
Well off to the salt mines..
Gary
3 rows in front of the bleachers for plays and such. Probably very close to the stage area, right? I dont think I would be concerned about aiming / moving the speakers behind them. They are within regular vocal projection, assuming that their teacher has told them that they're in a play and have to TALK LIKE THIS. Better that 1/2 the people hear really well than all hear skwat. Some times you have to live within the parameters that you're given. And I know that if I were in your shoes now, I'd be pulling my hair out because I expect nothing less than perfection, even if it's not possible.
Good luck,
DRA
Thanks for clarifying the horns 'beaming' energy, that was the nib I was not grasping.
Kevin has posted the mode numbers here, but I don't know how to evaluate them, so could use your help on that.
http://www.teamaai.net/kevin/jay/GymRoomModes.doc
I'll have to digest what you have said for a bit. I like the idea of a center cluster.
Dra -
You pegged my sentiments exactly on the chair seating area. The stage is almost right by the front row and yes the kids better project their voices. Plus the overhead speakers will add some to those setting in the chairs. The way things are now, we are basically sacraficing the majority of listeners for a few people right off of the stage area. I appreciate your ability to extrapolate this information into very useful observations. You've got a real nack for that.
I'm gonna go check and see if the power is on in the gym.
Catch you all later!
Room Dimensions
If you have not yet built a room, or you're about to refinish a space such as a basement, you can do a \"what if\" analysis to determine the room dimensions that will create the fewest problem frequencies. This is why I included a row at the bottom of the spreadsheet that flags problem frequencies and places the total count in cell B27. The \"what if\" analysis procedure begins with the Modal Distribution table and the Ceiling Calculator table. (A good example is described in the March/April '99 \"HTA.\") Alternatively, you can just start entering numbers (in inches) into cells C4 through C6 to look for dimensions that minimize the number of problem frequencies.
If you already have a home-theater room, you can just plug in its dimensions (in inches) into cells C4 through C6; the spreadsheet does the rest. One caveat: Make sure you follow the advice in the November '98 \"HTA\" on how to measure the size of your room. The dimensions in the spreadsheet I've provided are the ones from the \"As Built\" theater in the March/April '99 \"HTA\" with the seating position 1/3 of the way from the back wall, side wall, and floor.
As Built
Room Dimensions 294.5 x 294.5 x 147 inches (L x W x H)
Distance from each wall 98.17 x 98.17 x 49.00 inches (Back x Side x Floor)
Keep in mind that the problem frequencies in row 27 are only a problem if the seating position puts the listener in a null or peak for them. Of course, if there are many problem frequencies (such as the 19 instances in the \"As Built\" dimensions), it is difficult or impossible to pick a good seating position. The number of problem frequencies can be significantly reduced if the room's dimensions are chosen well to begin with.
Placement of Seats
Once you've determined the proper room dimensions, you can figure out good spots to place your seats. Enter the seating distance from the back wall, side wall, and floor into cells C12 through C14. The placement of the seating makes a big difference in the sound because different frequencies have peaks and nulls in different spots in your room. To try this out, enter into the spreadsheet the following dimensions (they're from my own home theater):
My Home Theater
Room Dimensions 224.5 x 165.5 x 94.375 inches (L x W x H)
Distance from each wall 75 x 83 x 32 inches (Back x Side x Floor)
My head is positioned one third of the room's length from the back of the room, exactly in the middle of the room's width, and approximately one third of the height above the floor. For my room and seating position, the following frequencies have peaks at my main listening position:
Room Length 90.5 181.0 271.6 (Harmonics 3, 6, and 9)
Room Width 81.9 163.7 245.6 (Harmonics 2, 4, and 6)
Room Height 215.3 (Harmonic 3)
When choosing seat locations, try to avoid positions at which a frequency has a double or triple peak. The January '99 \"HTA\" discusses a room with several such peaks. My seating position has no double or triple peaks at all. I have included a table in the spreadsheet that automatically calculates the double and triple peaks. If you're interested in these calculations, they start in cell AJ86.
Placing the listener in a null for a particular frequency is even more problematic than a peak. As described in the January '99 \"HTA,\" if a listener sits in a null, there is no way to compensate for this. An equalizer can be used to reduce peaks, but you can't boost the frequency in a null.
Again, consider \"My Home Theater\" dimensions and seating position. The seating position is exactly in the middle of the room's width. The diagram on page 48 of the January '99 \"HTA\" shows the peaks and nulls for the first eight axial modes. It is clear that the halfway point in a room includes nulls at the 1st, 3rd, 5th, and 7th harmonics for that dimension.
You must avoid seating positions at any nulls. By selecting the right seating position (even if you have a room that is merely okay acoustically), you can achieve better sound. My seating position coincides with nulls at several frequencies, so I am looking at ways to change my seating position relative to the width of the room. I have included a table that automatically calculates single, double, and triple nulls.
I got you covered.
Remember you're not reinventing the entire gain structure here. So don't make the anxiety more than it needs to be. Remember also that you know what you are doing. You've proved that already. This bit of adjustment will be easy by comparison. I also think you will be delighted with how easy it is to rough in the sound with your new desk. You've made a good choice there and you will see why by going through this process.
I look forward to hearing about your adventure.
Take care!
The power is back up and the speakers are down.
I'm shopping for hardware today. Putting them back up Wed PM.
Here's the deal... I was able to duplicate problem twice and then isolate it today... It appears that the power supply in the new mixer is bad... I spoke with the manufacturer (Allen & Heath) tech-support and they asked me to return it for a new unit via the distributor... I called the distributor and they told me I purchased the last unit they had in stock... The distributor is contacting Allen & Heath to see how they can get us a replacement unit ASAP...
I thank you very much for your support,...and for using your valuable time in helping me work the problem...:)
Kevin
I'm curious: What did you decide in regards to speaker placement, etc.?...
Kevin
Kevin
DRA
They told me they have never experienced this problem before... The power supply goes bad after the unit has been turned-on for a while...like two to four hours... Then if the unit is turned-off for a couple minutes and then turned back on it will run for another two hours...
Kevin
I tried this but I couldn't get enough volume for the drummer due to the distance... I think the following might be the solution to our problem: http://www.rolls.com/products/pm52.php
I contacted Rolls directly and covered my bases ie...amp wattage and impedance, headphone impedance, etc.,...and they claim this puppy is very robust and will handle practically anything I throw at it...
Kevin
How did your speaker relocate go? What does it sound like?
Kevin
Just a suggestion, but perhaps we should move Wolfies install to a different thread? This puppy is approaching biblical proportions.. as to what happened I don't know kevin? Perhaps we were spammed? Connie didn't tell me of anything when you saw all those posts.. perhaps she just handled it.
:shock:
I'm talking with her now to see if I can't get a \"READ THIS BEFORE POSTING\" banner so we can address some of the more problematic areas of the \"newbie\" posters.. like lack of info...some primers perhaps, links to the old forum, and training vids.. any suggestions what you would like to see?
Well I'm off.. be well
G
1- How to do a generic custom set-up for speakers and amps.
2- How & why to do a gain structure.
3- How to use PEQ's to \"tune\" problem passive cabs.
4- How to properly set x-overs for different cab combos. How to determine the Lo-cut / Hi-pass filter.
5- How & why to use output limiters.
6- How to eliminate feedback.
7- DRPA vs DR260
8- Complete list of manufacturer speaker tunings for passive cabs. (empty with a brief explanation why)
DRA
I'm fine with it,...even though I really enjoy the company...:)
A few more suggestions:
9- How to time align your mains and subs (I would enjoy writing something on that)
10- How to incorporate PEQ in suppressing feedback
11- How to map-out speaker placement for optimum sound quality
12- How to calculate \"insertion loss\" and proper wire sizing for 8-ohm, 4-ohm, or 2-ohm speaker runs (I would enjoy writing something on that)
Kevin